Common oscillatory modes in geomagnetic activity, NAO index and surface air temperature records

Detection and extraction of quasi-oscillatory dynamical modes from instrumental records of geophysical data became a useful tool in analysing variability of observed phenomena reflected in complex, multivariate geophysical signals. Using the extension of the Monte Carlo Singular System Analysis (MC SSA), based on evaluating and testing regularity of dynamics of the SSA modes against the colored noise null hypothesis, we demonstrate detection of oscillatory modes with period about 96 months in the long-term records of aa index as well as in the records of surface air temperature from several mid-latitude European locations and in the North Atlantic Oscillation index.